Add a method to slim to single emoji set

[billy1380]

Currently all emoji sets are compiled (I think), this makes gwt deployments very slow and not great for people who are planning on using only a single set.

Try to find a way to specify a single emoji set and remove the rest.

[billy1380]

This is probably not required since, emoji is becoming ubiquitous. There is no keyboard support so the keys/names are important, all that is required is to replace them with the unicode mappings.